A recent meeting underlined the continual freshness of studying the ancient history of the universe. Cosmology, which studies the structure of the universe, has been developing rapidly in the past few decades. The number of articles on cosmology, astrophysics and even astronomy in recent issues of CERN Courier testifies to this. Improved observational means and an increased understanding of particle phenomena in the early universe have transformed cosmology from a speculative philosophy into an exact science, yielding diversified knowledge about the laws of nature.

In 1997 particle physicists interested in cosmology recognized the need for a regular workshop dedicated to particle astrophysics and particle cosmology. Particle astrophysics includes, in broad terms, studies of and searches for relic particles and other remnants from the early universe constituting dark matter, as well as neutrino astrophysics, which gives important information about neutrino properties. Particle cosmology deals with particle aspects of the physics of the very early universe: inflation, reheating, cosmological aspects of Grand Unified Theories and strings, baryogenesis, phase transitions and other aspects of symmetry breaking. To complete the picture, particle physicists also need to make contact with purely gravitational issues, with the possible need to rewrite general relativity and with purely astronomical work leading to the determination of cosmological parameters.

The first workshop in the series, COSMO-97, was held in the Lake District, England; COSMO-98 was held in Asilomar, California; COSMO-99 was held in Trieste, Italy; and COSMO-2000 was held in Cheju Island, Korea. This year's meeting, COSMO-01, was held in Rovaniemi, Finland, right on the Arctic Circle, on 30 August - 4 September. In Finland, research in cosmology started in the early 1980s and today it is one of the most fruitful research fields in the physics department of the University of Helsinki and in the Helsinki Institute of Physics. New impetus and new resources have arrived since Finland joined the European PLANCK project, in which Finnish theoreticians and instrument builders have specific responsibilities.

The Rovaniemi programme comprised 33 invited plenary talks and 63 contributed talks in two parallel sessions. The plenary speakers treated aspects of inflationary cosmology, quintessence cosmology, string cosmology, extra dimensions, the ekpyrotic universe, baryogenesis, Big Bang nucleosynthesis, phase transitions, the angular power spectrum of the cosmic microwave background, large-scale structure, magnetic fields, dark matter, cosmological parameters, neutrino astrophysics and ultrahigh-energy cosmic rays.

The proceedings of the workshop will be published in the SLAC electronic conference proceedings archive and in the Los Alamos arXive astro-ph. Meanwhile, all of the presented material in both plenary and parallel sessions is linked to the workshop Web site at http://www.physics.helsinki.fi/cosmo_01.

The next workshop in this series will be held on 18-21 September 2002 in Chicago.